Mirrors Edge like edge grab in Quake C

// by daemonicky
// comments are translated
// I may have put some errors while dumping this code
// I apologize for them


void() PlayerPostThink =
{
    if (PlayerDoGrab(PLAYER_RADIUS))
        {
          // player grabbed onto ledge or something
...

//
// declarations and globals
//

float GRAB_EYE_UP = 10; // how much from origin eye is
float GRAB_HAND_UP = 15; // how much from origin hand is
float PLAYER_LEGS = 24;
float PLAYER_RADIUS = 32;
float PLAYER_HEIGHT = 56;//24 /* PLAYER_LEGS */+ 32;

float grab_can;
float grab_z;

float(vector _origin, float _radius, vector _angles) PlayerCanGrabOne;
float(vector _origin, float _radius, float _n) PlayerCanGrabAround;


....


float(float _radius/*hack*/) PlayerDoGrab =
{
        // the grabbing itself
    if (grab_can)
    {
                // there is a chance it is safe and
                // does not causes problems
                // i do not know for sure
        if (TRUE)
        {

            local vector SafeOrigin;
            SafeOrigin = self.origin;
            SafeOrigin_z = grab_z;
            setorigin(self,SafeOrigin);
        }
        else
        {
                // unsafe
            self.origin_z = grab_z;
        }
        self.velocity_z = 0; // gravitation is always applied so do this
        // TODO: make it less rigid
        self.velocity = self.velocity * 0.5;
    }

        // always test
    if (PlayerCanGrab(_radius/*hack*/))
    {
        // for first time- turned on
        if (!grab_can)
        {
            // it was set
            grab_can = TRUE;
            // remember height
            grab_z = self.origin_z;
            PlayerStop();

            // possible alternative : self.movetype = MOVETYPE_FLY;
        }
    }
    else
    {
        grab_can = FALSE;
    }
    return grab_can;
}

float(float _radius/*hack*/) PlayerCanGrab =
{
    return PlayerCanGrabAround(self.origin, _radius/*hack*/,  4 * 4);
        // was threre, but not so cool
    // return PlayerCanGrabOne(self.origin, _radius/*hack*/, self.angles);
};



float(vector _origin, float _radius, vector _angles) PlayerCanGrabOne =
{
    local vector Eye;
    local vector Hand;

    // remove pitch
    /* v_forward = */ makevectors('0 1 0' * _angles_y + '0 0 1' * _angles_z); //
    Eye = _origin + v_forward*_radius + v_up *GRAB_EYE_UP;
    Hand = Eye;
    Hand_z += GRAB_HAND_UP;

    if (FALSE) // debug
    {
        particle(Hand, '0 0 0', 1, 10);
        particle(Eye, '0 0 0', 2, 10);
    }

    // eye is inside wall
    traceline(_origin, Eye, TRUE, self);
    if (trace_fraction == 1.0) //
        return FALSE;

    // hand is free
    traceline(_origin, Hand, TRUE, self);
    if (trace_fraction != 1.0) {
        return FALSE;
    }
    //bprint(" grab");
    return TRUE;
}

float(vector _origin, float _radius, float _n) PlayerCanGrabAround =
{
    local vector v = '0 0 0';
    while(v_y < 360)
    {
        if (PlayerCanGrabOne(_origin, _radius, v))
            return TRUE;
        v_y += 360/_n;
    }
    return FALSE;
}